Permanent magnets are used in a wide variety of fields, including electronics, information and communications, industrial and automotive electric motors, etc. With regard to the permanent magnets, further enhancement in performance and further reduction in size and weight are demanded. Presently, Nd2Fe14B compounds (neodymium magnets) are widely used as high-permeance magnets, and various proposals have been made for the purpose of further enhancement in performance.
One approach for such performance enhancement is disclosed in Japanese Patent Application Publication No. 2003-59708 (JP-A-2003-59708). Japanese Patent Application Publication No. 2003-59708 (JP-A-2003-59708) describes a nanocomposite magnet in which a soft magnetic phase with high magnetization and a hard magnetic phase with high coercive force are uniformly distributed in the same metallic structure and the soft and hard magnetic phases are magnetically coupled due to an exchange interaction. This nanocomposite magnet is produced as follows. That is, a raw alloy melt is rapidly cooled to prepare a rapidly solidified alloy. Then, the rapidly solidified alloy is thermally treated to disperse Fe fine particles in the hard magnetic phase, thus producing a nanocomposite magnet. The patent application says that by controlling the condition of the thermal treatment, a minute Fe phase is dispersed in the nanocomposite magnet.
However, the foregoing method has the following problem. That is, depending on the thermal treatment condition, the crystal grain of Fe becomes rough and large, and the method is not suitable for an industrial technique that requires large-volume synthesis.